Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
  • B29C45/47—Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
  • B29C45/50—Axially movable screw
  • B29C45/52—Non-return devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B7/00—Mixing; Kneading
  • B29B7/30—Mixing; Kneading continuous, with mechanical mixing or kneading devices
  • B29B7/32—Mixing; Kneading continuous, with mechanical mixing or kneading devices with non-movable mixing or kneading devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B7/00—Mixing; Kneading
  • B29B7/30—Mixing; Kneading continuous, with mechanical mixing or kneading devices
  • B29B7/34—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices
  • B29B7/38—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary
  • B29B7/40—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with single shaft
  • B29B7/42—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with single shaft with screw or helix
  • B29B7/421—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with single shaft with screw or helix with screw and additionally other mixing elements on the same shaft, e.g. paddles, discs, bearings, rotor blades of the Banbury type
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
  • B29C45/58—Details
  • B29C45/581—Devices for influencing the material flow, e.g. "torpedo constructions" or mixing devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/362—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using static mixing devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
  • B29C45/47—Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
  • B29C45/50—Axially movable screw
  • B29C45/52—Non-return devices
  • B29C2045/524—Flexible valves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
  • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils

Definitions

• the invention relates to a dispersion device for plastic or colouring material, comprising means for feeding the material under pressure, preferably a plasticising screw of the type which has apertures in the screw thread for the return flow of the material.
• a plasticising screw of the type which has apertures in the screw thread for the return flow of the material.
• Conventional plasticising screws in extruders or injection moulding machines have a specific finishing zone, the volume of which is less than the thread volume at the material intake. This difference in thread volume is specified as the screw compression ratio, and this ratio varies for different thermoplastics in dependence of melting properties, viscosity, and the volume ratio between the material in the cold granulated form and in the form of a homogeneous melt.
• the compression ratio can vary e.g. from 1.5:1 to 5:1.
• Plasticising screws can be designed in different ways so as to give a certain compression ratio, but the object of compression is always, inter alia, to create a certain back pressure in the plasticising screw, which affects the incipient melt during its feed towards the finishing zone where the material should have reached a homogeneously molten state.
• the back pressure can be influenced by hydraulic means, but this facility is not available in an extruder. Instead a so called screen plate is placed in front of the end of the plasticising screw, this screen plate being provided with fine-mesh screen cloths which are able to raise the back pressure in the plasticising screw.
• the group of screens obtained thus influences homogenisation.
• a non-return valve at the end of the plasticising screw so as to prevent the material flowing backwards in the screw thread during the actual injection process.
• a sel f closing nozzle so as to prevent injection of the material from the machine during the plasticising operation proper, during which the plasticising screw retracts in position so as to bring about a new injection stroke during which the plasticising screw is pressed forward like a piston.
• the self-closing nozzle can consist for example of a movable valve nozzle or a spring-loaded piston inside the injection nozzle and it can also consist of a ball valve or a hydraulically operated piston .
• none of these arrangements is envisaged to provide increased dispersion and homogeneity of the material and they cannot be employed for this purpose. Furthermore, they are of such nature that they cannot be modified for use in an extruder.
• FIG 1 is an axial sectional view of the front portion of an extruder with a dispersion valve accord ing to the invention
• FIG 2 is a diagrammatic view which illustrates the flow of material with the dispersion valve open
• FIG 3 is a view corresponding to FIG 1, with a modified dispersion valve
• FIG 4 is an axial sectional view of the front portion of an injection moulding machine with dispersion valve in accordance with the invention
• FIG 5 is a fragmentary axial sectional view of a cylinder with a plasticising screw provided with a dispersion valve in accordance with the invention at its front end
• FIG 6 is an axial sectional view of an adaptor which is designed for incorporation in an injection head of an injection moulding machine and is provided with a dispersion valve in accordance with the invention
• FIG 7 is an axial sectional view of a dispersion valve with spring loaded washer of modified design
• FIG 8 is an axial sectional view of a dispersion valve which is mounted in an extruder die.
• FIG 1 illustrates the front portion of an extruder which comprises an extruder cylinder 10 with a plasticising screw 11 arranged rotably therein, preferably of the type specified, above with apertures in the screw thread for the reverse flow of the material being plasticised.
• a conventional extruder head 12 for extrusion of tube or pipe is provided on the machine.
• a displacement sleeve 13 is provided between the plasticising screw 11 and the extruder head 12 . Between the end of this sleeve, which faces the plasticising screw, and the cylinder 10 a dispersion valve in accordance with the invention is clamped, at the location where a conventional screen plate is usually mounted.
• This valve incorporates a seat 14 with a flow aperture which in this case is smaller than the actual screw diameter but which can also be made larger than the screw diameter. The aperture can be tapered so as to facilitate flow.
• the valve comprises a screen washer 15 which has no hole in the centre and which instead is provided with two small torpedoes 16 and 17. These torpedoes are pointed and are directed axially.
• a truncated conical spring washer 18 is located, contacting the seat 14 at a certain bias.
• the bias is adjusted to the force which is required to produce an adequate specific pressure in the plasticising screw or to achieve an adequate dispersion in the valve proper.
• the spring washer is replaceable. As such it does not need to be truncated and conical but right from the outset can be. plane and be given the truncated conical form by the washer being clamped when assembled on the supporting torpedo.
• the conventional screen plate which can be regarded as a common low-pressure arrangement in the extrusion process has thus been replaced by a more modern high pressure equipment.
• the screen washer 15 can be provided with one or more screen cloths 19 in the conventional manner.
• the pressure thus generated by the screw can vary from a few atmospheres to several hundred atmospheres gauge pressure, and it can be adjusted to the maximum positive pressure which the screw is able to generate by its conveying force.
• the spring washer opens by elasticity and leaves a thin gap between the seat and the contacting edge of the spring washer, the plasticised material flowing through this gap as a thin film at high flow velocity to pass subsequently through the screen cloths 19, the screen washer 15 and the displacement sleeve 13 to the extruder head 12.
• FIG 2 shows diagrammatically the flow of material through the dispersion valve by arrows F. It can be seen that material flows approximately radially outwards through the gap.
• the dispersion valve can be so designed that the screen washer 15 with the screen cloths 19 is located on the other side of the spring washer than that illustrated here, or the dispersion valve can be provided with a screen washer and associated screen cloths on either side of the spring washer.
• displacement sleeve 13 can be designed in different ways and can also be completely dispensed with, e.g. if a profile die is to be mounted instead of the tube head illustrated, without the dispersion being less effective thereby.
• the spring washer 18 is placed in such a way that the large end thereof, i.e. the concave side, faces the screw, i.e. the direction from which the pressure is applied. However, it can also be rotated half a turn so that the concave surface faces the unpressurized outlet and the convex surface of the spring washer faces the pressure side, i.e. the plasticising screw 11.
• FIG 3 which otherwise corresponds with the design shown in FIG 1.
• a seal is obtained by means of the spring washer acting as a non-return valve, e.g. when there.
• the dispersion valve in accordance with the invention retains the gas at a high internal pressure and if the valve is combined with a plasticising screw of the type which has apertures in the screw thread, also a better mixing and homogenisation of gas and melt is obtained.
• the dispersion valve prevents expansion in the plasticising screw proper.
• the gas is released only when the material passes through the gap between the spring washer 18 and the seat 14, i.e. at atmospheric pressure on the unpressurized side. All available types of propellant are gaseous at atmospheric pressure and at room temperature. The expansion of the gas in the plasticising screw is thus impeded by an internal overpressure corresponding to the plasticising temperature.
• FIG 5 shows the front portion of an injection moulding machine with an injection head 20 and an injection nozzle 21 mounted therein.
• the plasticising screw 11 is provided with a conventional non-return valve 22 at its front end.
• the non-return valve 22 can be replaced by a dispersion valve in accordance with the invention in the manner illustrated in FIG 5; this dispersion valve can be provided in combination with a conventional head or be combined with a head with a dispersion valve as shown in FIG 4. If the dispersion valve in FIG 5 is combined with the dispersion valve in FIG 4, two dispersion processes take place, independently, and in many cases this can be advantageous. Two dispersion processes separated from each other can also be arranged in an extruder by locating a dispersion valve in accordance with FIG 1 in front of the screw and a dispersion valve in the die proper or in connection with the head. In such a case the two dispersion valves are stationary, whilst on the other hand in the injection moulding method one is stationary in accordance with FIG 4 whilst the other is movable together with the plasticising screw shown in FIG 5.
• the dispersion valve as shown in FIG 5 includes a pin 23 which is screwed into the plasticising screw 11 and supports the spring washer 18 at the large end thereof, i.e. with the concave side facing the plasticising screw.
• the spring washer 18 rests against a ring 24 at one end edge thereof said ring being displaceable in the cylinder 10, whilst the other end edge of the ring 24 rests against the seat 14 which is mounted by means of the pin 23 on the plasticising screw 11. Under the pressure of the plasticised material a gap is thus formed between the spring washer 18 and the ring 24 on one hand and between the ring 24 and the seat 14 on the other hand, whereby two thin films of the plasticised material are formed.
• these thin films can be matched, by suitable choice of spring washer 18 and by combination of two or more spring washers.
• the flow velocity is extremely high and a dispersion is achieved which greatly surpasses that which has been obtainable previously.
• the advantage of the dispersion valve in accordance with the invention when this is arranged as shown in FIG 4, is that on one hand it brings about a counter-pressure inwards in the screw and on the other hand brings about simultaneous dispersion in the manner described here, preventing semi-molten or poorly dispersed particles making their way past the non-return valve, because the narrow gap does not permit this.
• the high internal pressure and the narrow gap in combination, force the non-molten particles to disperse with the remaining melt.
• the non-molten particles which by chance reach the dispersion valve are thus forced to change into the plastic state if they are to be able to pass through the narrow gap in the dispersion valve.
• the dispersion valve is arranged as an insert in the actual extruder or injection moulding machine. However, it can also be arranged as an adaptor as shown in FIG 5.
• the dispersion valve is located in a nipple 25, the seat being formed by a conical surface 26 in the nipple. This has a threaded hollow stud 27 so that it can be screwed into the head, whilst the nozzle 21 is screwed into the nipple.
• the nozzle here serves to hold the screen washer 15 inside the nipple 25 and it is thus possible to remove the screen washer with the spring washer 18 for cleaning purposes or maintenance merely by unscrewing the nozzle 21.
• an electrical heater strip 28 is provided outside the nipple 25.
• the spring washer in FIG 7 is more stream-lined in shape and provides a larger contact surface against the seat than do the spring washers previously described.
• the stream-lined shape can be important with material which cannot withstand the formation of so called flow pockets, e.g. PVC, and the advantage of a larger contact surface is that a wider gap is obtained.
• the washer in FIG 7 is generally indicated at 29 and is made from spring steel. It consists of a conical section 30 which has its point facing towards and inserted into the aperture in the seat 14, whilst the curved surface of the section sealingly engages the seat.
• the large end of the tapered portion 30 joins, with a gentle radius, to the large end of a truncated conical ring-shaped section 31, whereby the washer is threaded on the torpedo 16.
• a washer of this type functions in principle as two conical spring washers placed against each other.
• FIG 8 illustrates a die which fundamentally can be used as a film blowing head or alternatively as a tube head for producing plastic foil or plastic tube, but the die shown in FIG 8 can also represent a bottle blowing die.
• a die of the type shown in FIG 8 always has a central mandrel holder 32 to which mandrels can be replaceably attached for different diameters of the tube or pipe which is to be produced. Either a number of bores 33, as shown in the lower portion.
• FIG 8 or a number of supporting webs 34, as shown in the upper portion of FIG 8, are arranged in the mandrel holder.
• the bores 33 or the interstices between the webs 34 permit the through-flow of the material with the central portion of the mandrel holder located in the centre of the flow of material.
• This section supports a mandrel 35 which is detachably fastened thereto, the latter being surrounded by a sleeve 36 and together with this it confines the nozzle gap through which the material is to be extruded.
• Both the material between the bores 33 and the web 34 can however deposit undesirable flow stripes (cords) in the finished product.
• a dispersion valve in accordance with the invention with a spring washer 18 which interacts with a seat 14 is arranged on the mandrel holder 32 in FIG 8 by being fastened to the mandrel holder by means of a screwed-on torpedo 37.
• the spring washer 18 is a high pressure washer and is adapted to bring about a high pressure backwards in the screw of the plasticising device.
• a further spring washer 18' which interacts with a seat 14' formed by the sleeve 36 and which is attached to the mandrel holder 32 by being clamped between this and the mandrel 35 which is threaded thereon.
• the spring washer 18 ' is smaller than the spring washer 18 and serves t o eliminate flow stripes and other marks after the mandrel holder. As a consequence thereof the complicated and rather unsatisfactory arrangements for elimination of such flow edges and marks mentioned above can be dispensed with.
• an intermediate pressure chamber is obtained between the two washers. During the manufacture of expanded products, expansion occurs in this intermediate pressure chamber. As mentioned above an extra spring washer may be required for dispersion of possible residual products left because of chemical reaction at the gas generation during expansion, and in the embodiment shown in FIG 8 the spring washer 18' carries out this function.
• the spring washer has a diameter of for example
• colouring pigments can be dissolved in oil, varnish or water and forced through the dispersion device in accordance with the invention for homogenisation and fine distribution of the colouring pigment.
• the device by means of which the material is fed under pressure be a screw, as this device can also be designed as a piston with a reciprocating motion. It should also be mentioned that the spring washer can be designed in one piece with the supporting torpedo.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20338702

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (2)

Family Cites Families (3)

• 1979
  • 1979-08-27 SE SE7907120A patent/SE426785B/sv unknown
• 1980
  • 1980-08-27 JP JP50193780A patent/JPS56501194A/ja active Pending
  • 1980-08-27 AU AU62262/80A patent/AU6226280A/en not_active Abandoned
  • 1980-08-27 WO PCT/SE1980/000218 patent/WO1981000525A1/en not_active Application Discontinuation
• 1981
  • 1981-03-09 EP EP80901623A patent/EP0034159A1/en not_active Ceased

Non-Patent Citations (1)

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